Summary of work: Studies of gender differences and individual variability in age-related phenomena are being carried out to: 1) determine the normalrange of variability in human aging, 2) identify potential sources ofvariability which may be responsive to intervention, and 3) determineif there are subgroups of individuals who are more susceptible orresistant to various aspects of aging. The research combines the useof sophisticated statistical methodologies and the unique time depthand multidisciplinary breadth of the existing BLSA data base toexamine issues related to the concepts of normal and successfulaging, as well as to increase the power of traditional researchdesigns. The statistical methods used include longitudinalregression models, time dependent proportional hazards analysis, andfinite mixture models. Results from these models can provide contributions to the theoretical and methodological development of biomedical risk factor studies, as well as to an increased understanding of the dynamics of the aging process. Research is in progress to develop more refined methods of studying variability in aging in order to develop theoretically and methodologically sound approaches to risk factor analysis which account for changes in an individuals covariates over time and the possibility that individuals differ in susceptibility or resistance to aging process. - Human Subjects: Interview, Questionaires, or Surveys Only